Personal authentication device

ABSTRACT

A compact authentication device that prevents user from feeling pressure and is strong against external light, when capturing an image of a finger blood vessel pattern with transmitted light. The device includes a guidance part for determining the finger position, a light source disposed on at least one side of the guidance part to emit light to be transmitted though the finger, an image capture part for capturing the transmitted light, a shading unit for limiting an irradiation region of the light, a finger thickness measuring unit, a unit for controlling a light amount of the light source based on a result of the measurement, a unit for recording registered image patterns of the finger, a unit for collating a captured image pattern from the image capture part with the registered patterns, and a unit for controlling different processing according to the collation result.

BACKGROUND OF THE INVENTION

The present invention relates to a personal authentication device usinga living body, and in particular a living body personal authenticationdevice based on a blood vessel pattern of a finger.

As a highly convenient security method that does not require to carry akey or the like and reduces the risk of illegal use due to loss or atheft, living body authentication using a part of a personal body, suchas a fingerprint, iris, or a blood vessel pattern, as a key isattracting attention. Among them, an authentication method using a bloodvessel pattern brings about little rejection symptom. Because theauthentication method does not remind us of crime investigation unlikethe fingerprint, and an eyeball is not directly exposed to light unlikethe iris. Furthermore, since the blood vessel pattern is not a livingbody surface, which can be easily absorbed, but is an internal feature,the authentication method using the blood vessel pattern has anadvantage that forgery is difficult.

Such a blood vessel pattern within a living body is obtained byilluminating a subject region with a infrared light source and capturingan image thereof with an image capture system, such as a camera or animage sensor, having sensitivity to infrared light. Since hemoglobin inblood absorbs infrared light well, light is absorbed in the blood vesselportion and the blood vessel portion appears dark in the image ascompared with peripheral tissues. A pattern obtained by a differencebetween the brightness and darkness becomes the blood vessel pattern.

There are two methods for capturing an image of the blood vesselpattern. One of the two methods is a reflection method of capturingreflected light. The other of the two methods is a transmission methodof capturing transmitted light obtained by illumination from the back.Such an authentication device is disclosed in, for example,JP-A-2002-083298.

In the reflection method, the light source and an image capture systemcan be disposed on the same side as one body. Thus, the reflectionmethod has an advantage that the device is housed compactly and thespace located across the finger from the device is not occupied,resulting in openness. In the case where reflected light is captured,however, light emitted from the light source is reflected by theepidermis not a little. The strength of light that arrives at thevicinity of the blood vessel located in the subcuteneous tissue, whichis located under the epidermis, and is reflected becomes relativelyweak. Therefore, the captured image lacks pattern clearness. As aresult, it is difficult to obtain a pattern having repeatability, unlessthe blood vessel is clear to such a degree that visual recognition ispossible even under the visible light, like a vein located in back of ahand having thin epidermis. This means that the pattern can bereproduced easily, and there is a serious problem as a securitytechnique in the aspect of forgery resistance. In addition, because ofthe property that reflection of light from the epidermis is intense, theinfluence of a change of the skin surface, such as an injury, skinchapping, or wrinkles, on the captured image is inevitably great.

On the other hand, in the transmission method, there is a limit in thethickness of a living body through which light can be transmitted.However, light emitted from the light source and reflected by theepidermis is returned only to the light source side, and the imagecapture system is not affected. The finger has just a thickness throughwhich light can be transmitted. In particular, as for the blood vesselpattern located on the palm side, the blood vessel itself is thin, andthe epidermis is also thick as compared with the back. Even if an imageof the blood vessel pattern is captured by a camera, therefore, thetransmission method is excellent in forgery resistance.

For capturing the transmitted light, however, it is necessary tointerpose the finger between the light source and the image capturesystem. If the light source part, the finger, and the camera part arearranged in a vertical straight line in the cited order as shown in FIG.9, therefore, the light source part hides the finger as if it is acover, when seen from the position of the eye at the time of operation.The authenticating user feels pressure because the user cannot see thefinger. Furthermore, if an operation button or the like is disposed inthe finger tip position, the user might waver in grasping the buttonposition. On the other hand, if the light source part, the finger, andthe camera part are arranged in a horizontal straight line as shown inFIG. 10, then there isn't anything, such as a cover, for hiding the topportion, and the finger can be seen from the viewpoint position.However, there is a problem that the hand that can be used forauthentication is limited to the left hand or the right hand accordingto the position relation between the light source and the camera. FIG.10 shows the case where the light source is disposed on the right side.If the hand is the right hand, then it is easy to turn the palm side ofthe finger toward the camera part. In the case of the left hand,however, it is necessary to forcibly wrench the arm to turn the palmside toward the camera part. In other words, in an authentication devicehaving a camera part on the left side and a light source part on theright side, authentication other than that using the right hand is notpractical. In the case of the opposite arrangement, authentication usingthe left hand is compelled. Of course, it is conceivable to prepare twosets each including a light source and a camera, symmetrically so as tobe associated with the right hand and left hand, respectively. However,there are many problems, such as a cost increase and necessity of cameraswitching.

As a solution to the problems, a method shown in FIG. 12 is conceivable.In this method, the light source, the finger and the image capturesystem are arranged in a vertical direction, but they are not arrangedsimply in the vertical direction. Light sources are disposed obliquelyabove the finger in the tilted state. As a result, the finger is nothidden from the eye position at the time of operation and the feeling ofpressure can be mitigated, as compared with the conventional verticalalignment method shown in FIG. 11. In addition, it is not necessary tolimit the hand to be used for authentication to the left or right hand.

Even if the light sources are disposed obliquely above the finger,however, side walls for supporting the light sources having theconventional height are needed, and feeling of pressure is left not alittle. In addition, the size of the entire device scarcely changes. Ofcourse, if the side walls are made lower, then the feeling of pressureis eliminated. Even in this case, light emitted from the light source toside faces of the finger is scattered inside, and consequently the lightalso reaches the palm side of the finger, which is not on the straightline in the incidence direction. In other words, transmitted lightexists on the palm side of the finger in the same way as the case wherethe light source is disposed on the back side of the finger. If thelight sources are disposed in low positions, however, light strikesdirectly palm side portions and the light is reflected. For the samereason as that in the reflection method, it becomes difficult to obtaina blood vessel pattern from each of the palm side portions. Since theamount of light reflected by the side face of the finger is large,regions in which the brightness is saturated at its maximum value areformed in the captured image and parts of the blood vessel pattern arelost, as shown in FIG. 13 as a typical example. If the output strengthof the light sources is adjusted, then the area of each of the saturatedregions can be restrained to be small. In that case, however, the lightamount reaching the vicinity of the center on the palm surface of thefinger conversely becomes insufficient, resulting in a problem that theblood vessel pattern cannot be obtained. In other words, unless theratio of the reflected light to the transmitted light is suitablyadjusted, a correct blood vessel pattern is not obtained. If the sidewalls are low, then external light other than the light emitted from thelight sources also strikes directly the side face of the finger sidewardor obliquely. This becomes a cause of aggravation in the authenticationperformance under the strong external light, such as the settingsunlight.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a compactauthentication device that prevents the user from feeling pressure andthat is strong against the external light, when capturing an image of afinger blood vessel pattern by using the transmitted light.

Another object of the present invention is to reduce the saturatedregions in the pattern obtained by capturing an image of the finger, andthereby provide a clear finger blood vessel pattern, in the case wherelight sources are disposed in the finger side face direction.

In order to achieve the objects, a typical example of the presentinvention disclosed in the present application will now be describedroughly.

A personal authentication device includes a light source for emittinglight to be transmitted through a finger, an image capture part forcapturing transmitted light obtained by applying the light emitted fromthe light source, and a unit for adjusting light amounts of thetransmitted light from the finger and reflected light from side faces ofthe finger.

Specifically, a shading unit limits an irradiation region as a unit forchanging the light amounts. Or light from a light source having a strongdirectivity, such as a laser, is focused on an upper side of the finger.Such a configuration will be disclosed.

Other objects, features and advantages of the invention will becomeapparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of a device form according to the presentinvention;

FIG. 2 shows an example of a device system configuration according tothe present invention;

FIG. 3 shows an example of a software flow according to the presentinvention;

FIG. 4 shows an example of a sectional view of a finger insertionportion in a device;

FIG. 5 shows an example of a device using a plane image capture system;

FIG. 6 shows an example of a device using a mirror when capturing animage;

FIG. 7 shows an example of a device according to the present invention;

FIG. 8 shows another example of a device form according to the presentinvention;

FIG. 9 is a schematic diagram showing problems of a conventional method;

FIG. 10 is a schematic diagram showing problems of a conventionalmethod;

FIG. 11 is a schematic diagram showing a change of a captured imageaccording to a light source position;

FIG. 12 is a schematic diagram showing a change of a captured imageaccording to a light source position;

FIG. 13 is a schematic diagram showing a change of a captured imageaccording to a light source position;

FIG. 14 is a schematic diagram showing a change of a captured imageaccording to a light source position;

FIG. 15 shows an example of a device using a mirror as a light source;

FIG. 16 shows an example of a device using a mirror as a light source;and

FIG. 17 shows data showing relations between a shading ratio and asaturated region.

DESCRIPTION OF THE EMBODIMENTS

Hereafter, an embodiment of the present invention will be described indetail.

Herein, a lower side of a finger means a surface of a palm side or animage capture part, and an upper side of a finger means a back side of ahand and a surface opposite to the surface of the image capture part. Aside face of a finger means a surface of the finger other than the palmside and the back side of the finger, or a surface other than the upperside and the lower side.

Herein, transmitted light means light that is transmitted through theinside of a finger, and the term “transmitted light” is used in meaningas distinguished from light reflected by the surface of the skin or theepidermis.

The saturated regions in the sides of the finger as typically shown inFIG. 13 are caused by light emitted from the light source and reflecteddirectly by the surface of the skin arriving at the camera. Unless theratio of the reflected light to the transmitted light is adjustedsuitably, a correct blood vessel pattern is not obtained. Hereafter, asolution according to the present invention will be described.

FIG. 1 is a schematic diagram of an authentication device according tothe present invention. On an upper side of a main body, there is a guidegroove 108 for exhibiting a place on which a finger 102 should be placedin an intuitively understandable form. Light source parts 104 aredisposed on the left side and the right of the guide groove 108. Theguide groove functions also as low side walls that hide the lower sideof the finger. Light sources are disposed within the device. Upper sidesof the light sources are covered. Light is applied to the finger placedon the guide groove 108 through a light source opening part 106. Thecovers disposed over the light sources also play a role in preventinglight scattered outside of the desired irradiation direction from beingreflected by fingers or the palm other than the authentication fingerand affecting the image capture as disturbance light. If the finger isplaced so as to be aligned with the guide groove 108, then there is abutton switch 118 in a position corresponding to the finger tip, andthere is an image capture opening part 110 in a position correspondingto regions located before and behind the first and second joints of thefinger. In this way, an image of the finger can be captured by a camera(image capture part) 112 disposed under the image capture opening part110. A filter for passing only the wave length of the infrared region ismounted on the camera (image capture part) 112 to restrain the influenceof light in the visible light region and capture an image of a bloodvessel pattern clearly. The image capture opening part 110 is covered bytransparent glass or acrylic plate together with the light sourceopening part 106 in order to pass light and prevent foreign substancesfrom getting in the authentication device. By using a plate of anoptical filter that passes only light in the infrared region instead ofthe glass or acrylic plate, two functions, i.e., device protection andvisible light reduction can also be put together in one sheet of plate.Furthermore, the chassis can be formed of an optical filter materialintegrally with the light source opening part and the image captureopening part.

The saturated regions in the side faces of the finger as shown in FIG.13 are generated by the fact that light emitted from the light sourceand reflected directly by the surface of the skin arrives at the camera.In other words, the saturated regions can be made smaller by absolutelyor relatively restraining the amount of light applied to the palm sideof the finger, i.e., the lower part of the finger in FIG. 13. In thepresent invention, therefore, the amount of light irradiated on aspecific region (especially the upper side of the finger) is adjusted,and thereby the area of the region saturated in brightness is reducedeven in an image captured by using the side face radiation method. Theproblem that a part of the blood vessel pattern is lost is thus solved.For example, the intensity and the amount of light irradiated on theupper part of the finger are increased.

Specifically, within each of the light source parts shown in FIG. 1, alight source 114 for emitting infrared light is mounted on a shadingplate 116. The shading plate prevents light from traveling to the lowerside of the finger, and serves as a yardstick of the position in whichthe finger is placed. The shading plate serves as a part of the guidegroove as well. By making the plane of the shading plate nearly coincidewith an optical axis of the light source and turn the optical axistoward the upper side of the finger, it becomes possible to shade lightfrom the lower side of the finger while efficiently using the strongestlight portion of the light source. If the slant of the shading plate ismade sufficient and the light source is placed on the bottom end side,then the light source is housed in a position lower than that of theguide groove, and the device can be made thin. At this time, the guidegroove including parts of the shield plates is subjected to surfacetreatment using a lusterless paint, material or pattern in order toprevent light reflected by the back side, i.e., the upper side of thefinger from being reflected by the guide groove again and applied to theside face of the finger. If the range in which the irradiation of lightis restrained is approximately ½ to ⅔ from the image capture part faceas compared with the width of the finger seen from the side face of thefinger, then an experimentally clear blood vessel pattern is obtained.

Herein, a direction pointed from the palm side of the finger to the backside direction in the case where the side face of the finger, which isneither the palm side nor the back side, is seen is referred to asheight direction. A direction pointed from a tip to a root of the fingeris referred to as width direction. Data measured when the shading areaof the finger side face is changed in the height direction from theplane of the image capture part with the finger width in the widthdirection fixed are shown in FIG. 17.

FIG. 17 shows data obtained by measuring the relation between the ratioof the range in which the light irradiation is restrained to the entireside face of the finger (shading ratio of the finger side face) and theratio of the saturated regions to the image capture part face of thefinger (ratio of the saturated regions to the finger belly), withrespect to twelve subject fingers.

It will be appreciated from this graph that there are slight variationsdue to individual difference. In the case where the finger side faceregion of approximately ⅔ from the image capture part face is shaded,however, the saturated regions disappear. It will be appreciated thatthe saturated regions can be restrained to approximately 10% when thefinger side face region of approximately ½ is shaded. If the lightsources are disposed so as to apply light to the upper side of thefinger side face as if the upper side is looked up from below, then thestrength of light that reaches the lower side of the finger isrestrained, resulting in a higher efficient. The elevation angle at thattime can be obtained easily from a direction angle peculiar to the lightsource that indicates the degree of spread of light in the traveldirection, and the above described ideal shading ratio of the fingerside face.

Even if the shading plate serving as a structure is not used, reflectionfrom the lower side can also be restrained by focusing light from alight source having strong directivity, such as a laser, on the upperhalf of the finger although the cost becomes slightly higher. Even ifthe light sources are unchanged, it is also possible to control theirradiation direction so as to restrain the irradiation direction onlyto the upper side of the finger, or dispose a deflection plateimmediately before the image capture system to weaken light only in thedirection peculiar to the reflected light. In addition, there is also amethod of acquiring an image with the influence of the reflection fromthe lower side being relatively restrained, not by physically weakeningthe reflection from the lower side of the finger, but on the contrary,by applying stronger light to the upper side.

As heretofore described, it becomes possible to obtain a clear bloodvessel pattern by providing a unit for adjusting amounts of lightrespectively irradiated on regions of the upper side and the lower sideof the finger to optimum amounts, even if the position of the lightsource is not restrained to right above the finger. In the presentembodiment, the unit for irradiating light to the upper side of thefinger and shading light directed to the lower side is provided.However, the conception of the present invention is not strictly limitedonly to the upper side and the lower side. It is a matter of course thatthe conception of the present invention is to irradiate light to aregion of the finger required for obtaining an image capture pattern ofa vein and relatively restrain the amount of light directed to otherregions of the finger.

The user place the finger on the guide groove 108 and presses the buttonswitch 118. Thereupon, authentication is started. However, the buttonswitch is not indispensable, but the fact the finger has been placed onthe guide groove correctly may be sensed by using other means. Forexample, a touch sensor using a change of electrostatic capacity or anelectro-conductivity of a living body may also be used. Or it is alsopossible to monitor an image captured by the camera 112 in real time anddetect the fact that the finger has been placed by using imageprocessing. In the case of the touch sensor, however, the user does notalways respond in such a state that authentication is ready, andconsequently care is needed. By using the button switch, the user canexplicitly determine the start timing of the authentication processing,and the authentication system can be maintained in the stand-by stateuntil the button is pressed. This results in an advantage that powerconsumption can be reduced. In addition, the authentication function canbe naturally added to a conventional device that has conducted someoperation by using a button switch, without compelling the user to alterthe operation procedure. The button switch in this case is not limitedto a mechanical switch. For example, anything, such as a pressuresensor, may be used so long as contact is not caused until the userintentionally operates it.

The precision of the personal authentication can also be improved bymounting a pressure sensor, apart from the button switch, on thetransparent plate of the image capture opening part 110. If strongpressure is applied to a blood vessel of a living human being, then theblood vessel is crushed and spread. In other words, lines in the veinpattern become thick. If pressure is further applied, then the bloodflow is stopped and the blood vessel is lost to sight. If the fact thatsuch sequential changes peculiar to a living body are seen in thecaptured image when the pressure sensor responds is handled as aprecondition for authentication, then identity theft using a forgedfinger becomes very difficult and the safety is increased. Forauthentication, an image obtained before the blood vessel pattern islost to sight is stored in a buffer memory or the like, or an imageobtained after the finger is detached and the blood vessel pattern is insight again is captured and used. In a method of always monitoring thesequential changes according to the image and using the changes astiming for authentication, the pressure sensor is not needed.

FIG. 2 shows an example of a schematic block diagram of a systemconfiguration according to the present invention. The finger 102 isinterposed between a light source 114 and the camera 112, and an imagesignal of a blood vessel pattern is acquired in response to push of theswitch 118. The image signal of the camera 112 is converted to digitaldata by an image input unit 200. The digital data is stored in a memory208 via an input/output interface 204 in a computer 202. The switch 118is also connected via an input/output interface in the same way. Theon/off state of the switch 118 is stored in the memory 208. Or the sametime that the switch 118 turns on, an interrupt signal is issued to aCPU 206. Upon ascertaining that the state of the switch 118 has turnedon, or upon sensing the interrupt signal, a CPU 206 starts and executesa software program for authentication. On the basis of a result ofprocessing of the program, the CPU 206 conducts various kinds ofprocessing, such as displaying the result on a display unit 210, orsending a suitable signal to a control subject 214 to open or close adoor. A keyboard 212 is used to, for example, input auxiliaryinformation concerning authentication, such as a secret number.

Furthermore, in a personal authentication system, it is also possible toconduct various kinds of processing according to a collation resultbetween a vein pattern captured by the image capture part and aregistered pattern.

FIG. 3 shows an example of a software flow executed by the abovedescribed hardware, especially the CPU 206. In step 300, the wholehardware is initialized and initial values are substituted intotemporary variables needed to execute the program. If the shift to theinitial state is completed, the program comes in the idling state, andwaits for the switch 118 to turn on (step 302). If the switch turns on,then an image of the finger captured by the camera 112 is taken into thememory 208 (step 304). Image processing is conducted on the image datathus taken in, and a feature of the blood vessel pattern is extracted(step 306). A collation search is conducted to determine whether thereis a pattern that coincides with an already registered pattern (step308). The registered pattern is registered previously as follows. Priorto authentication, a legal registrant conducts the steps as far as thestep 306 in the same way, and then stores data in the memory 208 inassociation with information that identifies the registrant. The datathus stored is the registered pattern. As for the memory for registeringthe pattern, it is also possible to use a nonvolatile memory, in whichinformation is not lost by switching power supply, apart from the memoryfor processing execution. A recording medium, such as a hard disk, maybe used for the same purpose. If there is a coinciding pattern (step310), then a signal to the effect that a legal access right has beenauthenticated to a control subject, such as a device or a softwareprogram, that needs authentication, or authenticated personalidentification data is transmitted (step 312). If a coinciding patternis not found, then any signal is not transmitted, or a signal to theeffect that illegal access has been performed is transmitted as occasiondemands. And the standby state is continued until the switch turns onnext time.

The thickness of the finger varies according to individuals. If theamount of light is uniform, therefore, the blood vessel pattern appearswell in some persons, but it does not appear in others. The precision ofauthentication can be improved by continuously capturing an image withbrightness changed while controlling power supply to the light sourceuntil the blood vessel pattern appears most favorably. As for the powersupply control, for example, fast switching control, such as PWM (PulseWidth Modulation), using power transistors can be utilized. In addition,a sensor for measuring the finger thickness is added, then an optimumblood vessel pattern is obtained with a smaller number of capturedimages by previously calculating and storing the relation between thefinger thickness and the optimum amount of light.

The individual difference of the finger thickness closely relates to theshading performance. The reason will now be described. If the finger isthick, then the height of the finger becomes considerably higher thanthe shading plate, and the area of the side face of the finger exceedingthe shading plate becomes large. In this case, therefore, transmittedlight can be absorbed sufficiently. On the other hand, a possibilitythat light strikes the lower side of the finger as well occurs. If thefinger is thin, then the upper side of the finger does not exceed theheight of the shading plate. Since in this case, the area of a regionthat light strikes is small, a possibility of insufficiency in amount oflight occurs. In other words, in the case where the slant of the shadingplate is fixed, shading for the lower side of the finger becomesinsufficient if the finger is thick, whereas there is a risk ofinsufficiency in amount of light given to the upper side of the fingerif the finger is thin. Therefore, the direction of the light source maybe automatically adjusted according to the finger thickness by makingthe slant of the shading plate variable or using reflection from amovable mirror. As for detection of the optimum position in the casewhere automatic adjustment is conducted, it is possible, for example, tomonitor an image captured by the camera in real time, obtain the area ofthe saturated regions of the side faces of the finger, and effectcontrol so as to minimize the area in such a range that the blood vesselpattern appears clearly. It can be determined whether the blood vesselpattern is clear by determining whether the brightness ratio between ablack line representing the blood vessel and a white portionrepresenting peripheral tissues satisfies a certain fixed condition. Thearea of the saturated regions can be extracted as a region in whichpixels having the maximum brightness value are consecutive beginningwith the boundary vicinities of both sides of the finger. If the movablemechanism of the shading plate is further applied, then the light sourceparts 104, which swell like hills in FIG. 1, can be housed within thedevice chassis 100 except at the time of authentication. As a result,the device shape at the time of standby state is further thin and theprojections are eliminated. For example, the device becomes suitable formounting on a portable telephone or a personal digital assistant.

In addition, the saturated regions of the side faces of the finger canbe made to appear successively only on one side by turning on the lightsources disposed on both sides of the finger alternately. It is possibleto obtain an image of the finger free of saturated regions by capturingtwo sheets of image respectively captured at timing of turning on thelight sources, cutting out only half sheets of the image free of thesaturated regions in the captured images of the finger, and combiningthe half sheets free of the saturated regions to form one sheet ofimage. In the case of this method, the shading plate also becomesunnecessary. However, there is also the following trade-off. Since twosheets must be captured in succession in accordance with turning on ofthe light sources, it takes slightly longer time. Since the two sheetsof image are not always obtained with the same amount of light, aboundary between images becomes conspicuous in some cases. If smoothingis conducted so as not to make the boundary inconspicuous, thenclearness of the image is lost in some cases.

FIG. 4 is an enlarged view obtained by watching the guide groove 108, onwhich the finger is placed, from the side face in a variation of theauthentication device 100. On the bottom of the guide groove, there isthe image capture opening part 110. Under the image capture opening part110, there is a camera 112. The guide groove 108, on which the finger isplaced, may be flat. As shown in FIG. 4, however, the guide groove 108,on which the finger is placed, may be designed to draw an arc from theimage capture opening part 110 to a finger tip portion so that thefinger will be naturally bent. If it is attempted to stretch the fingerstraightly, then resultant strain of the skin of the finger presses theblood vessel and obstructs flow of blood, and consequently the bloodvessel pattern is not obtained in some cases. If the shape draws an arcas shown in FIG. 4, however, the finger is naturally bent, andconsequently the blood vessel is not pressed. Furthermore, in thenaturally bent state, the finger does not touch the surface of thetransparent plate in the opening part 110. Since there is no contactwith the surface of the transparent plate, neither the pressure of theblood vessel nor adhesion of stains is caused. Furthermore, by disposingthe transparent plate included in the opening part 110 in a lowerposition, or forming a finger rest 400 in order to lift the root of thefinger out of the opening part 110, it is also possible to morecertainly prevent the blood vessel from being pressed by contact betweenthe opening part 110 and the finger. Furthermore, by limiting the heightof the guide groove in the finger tip portion so as to just house thebelly portion of the finger tip therein, and opening the top part, evena person wearing fingernails long or wearing attached fingernails canplace the finger in a predetermined position without inconvenience.

FIG. 5 shows an example of an authentication device made thin. In theabove described device form, the camera is used to capture the image ofthe blood vessel pattern. Therefore, a focal length of a fixed length isnecessary. In addition, since the camera itself has a considerablethickness because of a lens and so on, the chassis of the image capturepart tends to be large. Therefore, the authentication device can be madethin by using a contact type image sensor. For example, as the contacttype image sensor, an array formed by arranging phototransistors havingsensitivity to infrared light in a lattice form is conceivable. Bysuccessively reading out values of the phototransistors, two-dimensionalimage data are obtained in the same way as the camera. In the case ofmolding that draws an arc as shown in FIG. 5, it becomes possible tomount phototransistors according to the curvature of the arc by formingthe phototransistors on a filmy flexible substrate. Furthermore, it isalso possible to replace the transparent cover in the image captureopening part 110 by the phototransistors.

FIG. 6 shows another example of the authentication device 100 made thin.By conducting camera image capture with a mirror 600 and thereby foldingthe travel path of light, it becomes possible to restrain the thicknessof the chassis, without changing the focal length of FIG. 4.

FIG. 7 shows an example in which the present invention has been appliedto an ATM (Automatic Teller Machine) of a bank or the like. Numeral 700denotes an ATM chassis. On a table-like operation plane, a display 702having a touch panel and the authentication device 100 are disposed sideby side. When drawing cash, the user first place a finger of one hand ona specified position of the authentication device 100. In that state,the user conducts operation, such as inputting an amount of money, withthe other hand according to messages displayed on the display 702. Theoperation is conducted in parallel with the personal authentication. Ifauthentication is attained, cash is output from a cash inlet/outlet 708.If authentication fails, then cash is not output, re-input is urged. Ifthe number of times of mistake is large, the transactions aretemporarily invalidated. Numeral 704 denotes a card slit. A cash card ora passbook 706 is inserted into the card slit 704 as occasion demands.When conducting personal authentication in a living body, the user istypically forced to conduct special operation causing stress, forauthentication. For example, in the conventional authentication of ablood vessel pattern of a finger, the user is required to insert afinger into a hole or a deep groove with a rejection symptom. Infingerprint authentication, it is necessary to press the sensor partwith force. In the case of iris authentication, the user must turn eyesto the sensor camera without winking. In the authentication device ofthe present invention, authentication becomes possible by only placingthe finger softly according to a shallow groove, which gives feeling ofopening. Therefore, it is hard to feel stress. Furthermore, sinceunreasonable force is not required, it is easy to conduct operation withone hand, while using the other hand for authentication. Even when anarithmetic operation device of lower cost is used or high precisionauthentication involving a larger amount of processing is conducted, itis possible to make the user unaware of the length of the processingtime if the authentication processing is completed within the inputoperation time for the amount of money or the like.

FIG. 8 shows another embodiment of the authentication device 100according to the present invention. The shading plate 116 is integralwith a rail 800. The rail 800 is linked to a spring 802. As a result,the shading plate 116 becomes movable so as to be absorbed into thelight source side of the side face. Such a groove as to just hide thelower side of the finger is formed between the shading plate 116 and theimage capture opening part 110. If the user attempts to place a fingeron the image capture opening part at the time of authentication, thennecessarily the shading plate is slid laterally. In this case, thespring 802 applies force to the shading plate to return it to theoriginal position. As a result, the shading plate comes in close contactwith the side face of the finger, and a higher shading effect for thelower side of the finger is demonstrated. If the user detaches thefinger from the authentication device, then the shading plate isautomatically returned to the original position by the spring, and theshading plate also functions to prevent dust and dirt of the imagecapture opening part 110. At this time, the shading plate can besmoothly slid by forming a notch 120 on this side of the shading plateand thereby slipping the finger from this side into the back side.Furthermore, when the user attempts the finger on the image captureopening part, it is also possible to guide the finger so as to positionit in the center of the image capture opening part by effecting controlwith a combination of a rack and a pinion so as to make the travelamounts of the left and right shading plates equal. If the same fingeris placed, the finger is placed in the same position wheneverauthentication is conducted owing to this guide function, resulting in ahigher collation precision.

FIG. 15 shows still another embodiment of the authentication device 100according to the present invention. A schematic structure around aportion on which the finger is placed is shown. In the example of FIG.15, light emitted from the light source is not applied directly to thefinger, but the light emitted from the light source 114 is changed indirection by a mirror 1500 and then applied to the finger. As a result,the degree of freedom in the position of the light source, fixingmethod, and wiring can be further increased, and the height of the sidewall can also be restrained.

In FIG. 16, the light source is disposed on one side of the finger, andthe mirror 1500 is disposed on the other side of the finger. Lightemitted from the light source 114 not only irradiates one side face ofthe finger, but also passes the finger and a space over the finger andarrives at the opposite side. This light can be reflected by the mirrorand used as a light source for illuminating the opposite side face ofthe finger. As a result, power consumption can be restrained as comparedwith the case where a plurality of light sources are used.

Heretofore, examples in which light sources are disposed in twopositions, i.e., on the left side and on the right side of the finger inorder to obtain a uniform and accurate blood vessel pattern have beenshown. However, the present invention is not limited thereto. If anecessary and sufficient performance is obtained, the light source maybe disposed on only either the left side or right side. This bringsabout an advantage in cost.

The present invention is not limited to personal authentication, but maybe combined with fingerprint authentication or the like. Since an imageof the fingerprint of the fingertip is also captured by a common imagecapture system, highly accurate personal authentication using aplurality of living body features becomes possible without increasingthe cost.

According to the present invention, light emitted from the light sourceor external light is applied to the lower side of the fingerexcessively. As a result, the image of the blood vessel pattern obtainedby capturing transmitted light becomes clear, and the precision of theauthentication can be improved.

It should be further understood by those skilled in the art thatalthough the foregoing description has been made on embodiments of theinvention, the invention is not limited thereto and various changes andmodifications may be made without departing from the spirit of theinvention and the scope of the appended claims.

1. A personal identification apparatus comprising: two light sources to irradiate light to a finger from two sides of the finger; a single image capture unit to capture the light from the light sources transmitted through the finger; and a processing unit to cause the two light sources to irradiate the light alternately, and cause said single image capture unit to capture a plurality of images at a timing of the irradiation of the light sources, wherein the processing unit extracts a feature of a vein pattern of the finger from the plurality of images captured by said single image capture unit due to said light irradiated by said two light sources and executes personal identification using the extracted feature.
 2. The personal identification apparatus according to claim 1, wherein: the processing unit extracts the feature of the vein pattern from unsaturated regions of the plurality of images which have saturated regions.
 3. The personal identification apparatus according to claim 2, wherein: the light sources irradiate the light so as to cause the saturated region in the images captured by the single capture unit.
 4. The personal identification apparatus according to claim 1, further comprising: a guide part for receiving the finger for causing the finger to arc along a length of the finger.
 5. The personal identification apparatus according to claim 1, further comprising: a measuring unit for measuring finger thickness, wherein the processing unit controls an amount of the light from the light sources based on a result of the measuring.
 6. The personal identification apparatus according to claim 1, further comprising: a switch located at a position corresponding to placement of a tip of the finger, wherein the processing unit initiates the personal identification when the switch is pressed by the finger tip.
 7. The personal identification apparatus according to claim 1, wherein: the single image capture unit and each of the two light sources are not opposite each other in a coaxial form.
 8. A personal identification apparatus comprising: a light source part to irradiate a finger with light from first and second sides of the finger; an image capture unit to capture images by the light transmitted through the finger; and a processing unit to cause the light to alternately irradiate the first side and the second side, and to cause the image capture unit to capture a plurality of images generated using the light from the light source part that irradiates the first and second sides of the finger at a timing of the irradiation of the light source part, wherein the image capture unit and the light source part are not opposite each other in a coaxial form, and the processing unit extracts a feature of a vein pattern of the finger using the images captured due to the light irradiated from the first side and the second side for personal identification.
 9. The personal identification apparatus according to claim 8, wherein: the captured images have a saturated region due to the light irradiated from the first side and the second side, and the processing unit extracts the feature of the vein pattern from a region of the images captured which is not saturated.
 10. The personal identification apparatus according to claim 8, further comprising: a guide part for receiving the finger for causing the finger to arc along a length of the finger.
 11. The personal identification apparatus according to claim 8, further comprising: a measuring unit for measuring finger thickness, wherein the processing unit controls an amount of the light from the light source part based on a result of the measuring.
 12. The personal identification apparatus according to claim 8, further comprising: a switch located at a position corresponding to placement of a tip of the finger, wherein the processing unit initiates the personal identification when the switch is pressed.
 13. The personal identification apparatus according to claim 8, wherein: the first and second sides of the finger correspond to right and left sides of the finger.
 14. The personal identification apparatus according to claim 8, further comprising a single said image capture unit to capture images by the light transmitted through the finger.
 15. A personal identification method comprising: irradiating light to a finger from two light sources disposed on two sides of the finger alternately; capturing a plurality of images by the light from the light sources transmitted through the finger at a timing of the irradiation with an image capture unit; extracting a feature of a vein pattern of the finger from the plurality of captured images generated using said light irradiated by said two light sources; and executing personal identification using the feature of the vein pattern extracted from the plurality of images, wherein each of the two light sources and the image capture unit are not opposite each other in a coaxial form.
 16. The personal identification method according to claim 15, further including the step of: extracting the feature of the vein pattern from unsaturated regions of the plurality of images which have saturated regions.
 17. The personal identification method according to claim 15, further including the steps of: measuring finger thickness; and controlling an amount of the light from the light sources based on a result of the measuring.
 18. The personal identification method according to claim 15, further including the step of: initiating the personal identification when a switch located at a position corresponding to a tip of the finger is pressed.
 19. The personal identification method according to claim 15, further including the step of: placing the finger in a guide part causing the finger to arc along a length of the finger.
 20. The personal identification method according to claim 15, further comprising a single said image capture unit to capture images by the light transmitted through the finger.
 21. A personal identification method comprising: irradiating a finger alternately from first and second sides of the finger with light; capturing images by the light transmitted through the finger a plurality of times at a timing of the irradiation by a single image capture unit; and extracting a feature of a vein pattern of the finger using the images captured by said single image capture unit due to the light irradiated from the first side and the second side.
 22. The personal identification method according to claim 21, further comprising the step: wherein the feature of the vein pattern is extracted from an unsaturated region of the images, having a saturated region, captured by the light irradiated from the first side and the second side.
 23. The personal identification method according to claim 21, further comprising: executing personal identification using the extracted feature of the vein pattern.
 24. The personal identification method according to claim 21, further comprising: measuring finger thickness; and controlling an amount of the light for irradiation based on a result of the measuring.
 25. The personal identification method according to claim 21, further including the step of: initiating the identification when a switch located at a position corresponding to a tip of the finger is pressed.
 26. The personal identification method according to claim 21, further including the step of: placing the finger in a guide part causing the finger to arc along a length of the finger.
 27. The personal identification method according to claim 21, wherein the step of irradiating the finger comprises irradiating right and left sides of the finger. 